WA Livestock Disease Outlook - for vets

Recent livestock disease cases in WA

Lupinosis and hepatic encephalopathy diagnosed in sheep with neurological signs

• Six of 1500 merino wether lambs died on a property in December, with a further 800 animals affected by signs of full mentation and/or a loss of condition.
• Sheep had been recently purchased from a Wheatbelt property, and had been grazing a lupin stubble for the past 6-8 weeks.
• A private vet examined two affected lambs that were both showing neurological signs, including facial twitching and apparent blindness. The lambs were recumbent and had difficulty rising.
• The private vet conducted a post mortem and submitted a full set of fixed and fresh samples to DPIRD. Information on appropriate sample collection can be found in the livestock disease veterinary sampling guide.
• Sheep or cattle showing neurological signs may be eligible for subsidy under the transmissible spongiform encephalopathy program (TSE). In this instance the sheep were under 18 months so they did not meet the criteria for the TSE program, however the vet was able to access a subsidy through the significant disease investigation program instead.
• On post mortem the submitting vet noted that both lambs had yellowing of the fat in the abdomen and enlarged kidneys with spotty discolouration of the cortices. One lamb had a yellow, swollen liver. An acinar/nutmeg pattern on the liver was seen in the other lamb.  
• Histopathological examination led to a diagnosis of lupinosis and there were changes in the brains consistent with hepatic encephalopathy. Both animals also had an interstitial nephritis.
• Blood results showed that both animals also had a vitamin E deficiency
• Additional testing ruled out lead toxicity, which also causes blindness and a dull mentation in sheep (and cows). 
• Read more about lupinosis in sheep and vitamin E deficiency in sheep.

Lumpy skin disease excluded in cow with skin lesions

• A private vet examined a 2-year-old cow with raised skin lesions covering the face and neck. The vet suspected bovine papillomavirus but wanted to rule out the exotic disease lumpy skin disease, which can cause widespread skin lesions. Samples were submitted to DPIRD and the submission was exempt from laboratory fees because a reportable disease was excluded.
• One cow from a group of 30 was affected (Figure 1).
• The private vet submitted fixed and fresh biopsies of the skin lesion.
• Histopathology confirmed cutaneous papillomas, thereby excluding lumpy skin disease. Electron microscopy revealed numerous papillomavirus particles (Figure 2).
• The laboratory diagnosis was cutaneous papillomatosis due to bovine papillomavirus.
• Bovine papillomaviruses are associated with cutaneous viral papillomas (cutaneous warts), fibropapillomas and squamous cell carcinomas in cattle, as well as sarcoid tumors in various other mammalian species.
• Warts in cattle can be caused by bovine papillomavirus 3, 5, 8 or 11. They commonly occur on the skin of young animals between 6 and 24 months of age. Usually they regress spontaneously as the cattle develop immunity to the virus but they may persist for up to 12 months in some animals, especially animals that are immunocompromised.
• The negative result for lumpy skin disease in this case helps to support WA’s market access by demonstrating freedom from the disease.
• Lumpy skin disease is a highly infectious disease of cattle caused by a poxvirus. It is mostly transmitted by biting insects.
• Lumpy skin disease is exotic to Australia. The international distribution of lumpy skin disease is increasing in range and it would have a significant impact on cattle productivity if it entered Australia. Clinical signs include multiple raised skin lesions, fever, salivation and nasal discharge.
• Read more about lumpy skin disease on the Emergency Animal Disease Bulletin No. 121

Figure 1. Cow with cutaneous papillomatosis lesions covering the face and cranial neck

Figure 2. Papillomavirus particles seen on transmission electron microscopy (negative stain)

In Autumn, watch for these livestock diseases

DPIRD disease investigation summary 2020

In 2020, the Department of Primary Industries and Regional Development investigated 1402 cases of disease in animals, primarily livestock.

Submissions were received from 77 private vet services and also government vets.

Disease investigations provide evidence that WA is free of livestock diseases that are reportable or affect trade. Submissions from vets also provide diagnostic information to aid producers in managing disease on their farms.

The exotic disease ehrlichiosis (E.canis) was detected in dogs in the State’s north for the first time in 2020. Vets submitted 513 potential cases of ehrlichiosis to the department for investigation of which 202 were positive for the disease.

Reportable disease exclusions

During 2020, there were 1056 reportable disease exclusions from 570 submissions. The most common reportable disease exclusions are shown in Figure 3.  E.canis is reported separately.

Figure 3. The top 10 reportable disease exclusions from laboratory submissions to DPIRD laboratory from January – December 2020. The orange bars represent the number of reportable disease exclusions from October – December 2020.

In 2020 there were 257 reportable disease exclusions in sheep. The number of reportable exclusions by region is shown in Figure 4. The most common reportable disease exclusion was scrapie with 48 submissions to the laboratory, some of the submissions involved multiple animals.

Figure 4. Reportable disease exclusions in sheep in 2020 by region. Exclusions are reported here at the submission level, not the animal level. Any given submission can have more than one disease excluded.

In 2020 there were 375 reportable disease exclusions in cattle. The number of reportable disease exclusions in cattle by region is shown in Figure 5. The most common reportable disease exclusion was Johne’s disease in cattle with 90 submissions to the laboratory.

Figure 5. Reportable disease exclusions in cattle in 2020 by region. Exclusions are reported here at the submission level, not the animal level. Any given submission can have more than one disease excluded.

In 2020 there were 87 reportable disease exclusions in pigs. The number of reportable disease exclusions in pigs by region is shown in Figure 6. The most common reportable disease exclusion was African swine fever and classical swine fever, with 27 submissions to the laboratory for each.

Figure 6. Reportable disease exclusions in pigs in 2020 by region. Exclusions are reported here at the submission level, not the animal level. Any given submission can have more than one disease excluded.

 The reportable disease exclusions in other species are shown in Figure 7.

Figure 7. Reportable disease exclusions in other species in 2020 by region. Exclusions are reported at the submission level, not the animal level. Any given submission can have more than one disease excluded.

Common endemic diseases in cattle

Common diagnoses in cattle in 2020 by region are shown in Figure 8.

Figure 8. Common diagnoses in cattle in 2020 by region. Diagnoses are reported at the submission level, not the animal level. Any given submission can have more than one disease excluded.

In the October – December quarter 2020

The most commonly diagnosed disease in the October – December quarter of 2020 in cattle was annual ryegrass toxicity (ARGT) with 6 submissions to the laboratory during this time (Figure 9). For more information on ARGT visit the webpage.

Figure 9. Common cattle diseases in October – December 2020 (blue) compared to the average number of submissions for the same diseases in October – December in the previous 5 years (grey).

Common endemic diseases in sheep

Common diagnoses in sheep in 2020 by region are shown in Figure 10.

Figure 10. Common diagnoses in sheep in 2020 by region. Diagnoses are reported at the submission level, not the animal level. Any given submission can have more than one disease excluded.

In the October – December quarter 2020

The most commonly diagnosed disease in sheep during October – December 2020 was helminthiasis with 10 submissions to the DPIRD laboratory (Figure 10). Annual ryegrass toxicity was diagnosed 7 times during this period.

Figure 11. Common sheep diseases in October – December 2020 (blue) compared to the average number of submissions for the same diseases in October – December over the last 5 years (grey).